Electromagnetic horn



1&5, 1956 .1.A. KQsTRlzA ELEcTnouAGNx-:Trc HORN Filed Aug. l, 1951 R:JOHN A KOSTR/ZA ATTORNEY nited States Patent O ELECTROMAGNETIC HORNJohn A. Kostriza, New Dorp, N. Y., assignor to International Telephoneand Telegraph Corporation, a corporation of Maryland Application August1, 1951, Serial No. 239,738

20 Claims. (Cl. 343-776) This invention relates to electromagnetic hornsand more particularly to electromagnetic horns for the propagation ofmicrowave energy.

One of the objects of the invention is to provide a simplified form ofelectromagnetic horn which does not require the precision of manufactureof previous microwave horns.

Another object of the invention is to provide a microwave horn that mayemploy as a part of the radiation system a wall of the chassis or otherapparatus associated therewith.

Still another object of the invention is to provide a microwave hornwhich is of a character readily adapted for the use of printed circuittechniques.

One of the features of the invention is the utilization of a basicprinciple present in a theoretically perfect parallel line transmissionsystem as described more extensively in patents to H. F. Engelmann, No.2,654,842 dated October 6, 1953 and to D. D. Grieg and H. F. Engelmann,No. 2,721,312, dated October 18, 1955. The present invention utilizesthis theoretically perfect parallel line system without requiring exactidentity and parallel spacing of the parallel conductors. The microwavehorn of the present invention employs two or more closely spacedconductors with one of the conductors, hereinafter sometimes referred toas the ground conductor, wider than the other conductor, hereinaftersometimes referred to as the line conductor, so as to produce, ineffect, an image of the line conductor in the ground conductor. Theso-called ground conductor theoretically might have a width extending toinfinity but for practical purposes need be only a little wider than theline conductor as long as its greater width provides for ampleconcentration of the electromagnetic iield between the opposed faces ofthe two conductors. The width of the ground conductor should beapproximately two or three times greater than that of the lineconductor, although it might preferably be wider if circumstancesprovide such an extended surface. Another feature is the varied hornconstruction that is made possible by use of the line-above-ground typeof transmission system and circuit printed techniques that may beemployed.

The above-mentioned and other features and objects of the invention willbecome more apparent by reference to the following description of anembodiment of the invention taken in conjunction with the accompanyingdrawings, wherein:

Fig. 1 is a view in side elevation of a horn in accordance with theprinciples of this invention;

Fig. 2 is a plan view of the horn shown in Fig. l;

Fig. 3 is a view in end elevation of the horn shown in Fig. l;

Fig. 4 is a View in side elevation of a horn similar to that shown inFig. 1 but comprising exponential variations in the thickness of thedielectric;

. Fig. 5 is a view in side elevation of a horn having a symmetricallinear variation;

Patented June 5, 1956 ICC Fig. 6 is a plan view of a horn according tothe invention incorporating matching posts;

Fig. 7 is a cross-sectional view along line 7-7 of Fig. 6 showing metalposts for determining the dielectric characteristic of the mediumbetween conductors;

Fig. 7a is a cross-sectional similar to Fig. 7 showing dielectric posts;

Figs. 8, 9, and l0 are plan, side, and end views, respectively, of ahorn array according to the principles of the invention; and

Fig. ll is a view in side elevation of a horn array according to theinvention.

Referring to Figs. 1, 2, and 3 of the drawings, the horn is shown tocomprise a termination of a transmission line made up of a lineconductor 1 proximate a ground conductor Z and separated therefrom by adielectric material 3. The line conductor 1 is energized with respect toground conductor 2 by a source of electromagnetic energy 4. Thedielectric in the vicinity of the horn is shown to be `linearly taperedas indicated at 5. The purpose of this taper variation of the dielectriccharacteristic is to provide an impedance match or transition betweenthe impedance of free space and the impedance of the transmission linecomprised of conductors 1 and 2. The are angle 6 of the horn may beselected to obtain certain desired directive launching eifects. Theconductor 1 is flared as indicated at la to provide the horn etfect, theconductor 2 being, in the embodiment of Figs. l, 2, and 3, a wide sheetof conductive material. lf desired, the conductor 2 may be a narrowsheet about two or three times wider than the width of conductor 1, withthe end portion ared similarly as part la. The line-ground conductors 1and 2 may be printed, embossed, or photo-engraved upon the dielectric 3.

Referring to Fig. 4, a side view of a horn is shown in which thedielectric material is divided at the end of the horn with the separateparts 7 varying in thickness eX- ponentially. The line conductor 1 andthe groundl conductor 2 are separated by a dielectric 3 and the sourceof electromagnetic energy is indicated at 4 similarly as in Fig. 1. Thepurpose of the two symmetrical, exponential variations in thickness ofdielectric is to provide a smooth transition from the impedance of thetransmission line to that of free space which is required for certainsymmetrical iield patterns desired of the horn.

In Fig. 5 a side view of a horn is shown in which the dielectric is alsodivided at the horn and the thickness of the separated parts 7a varylinearly and symmetrically. The line conductor 1 and the groundconductor 2 are energized by a source 4 as in Fig. l.

Figs. 6L 7, and 7a, which are plan and sectional views, respectively, ofan electromagnetic horn similar to that shown in Fig. 1 show matchingposts in the horn region where the dielectric in Fig. 1 is tapered. Thematching posts provide a better match between the electromagnetic wavespropagated between the line conductor 1 and ground conductor 2 and, inaddition, provide mechanical support near the mouth of the horn for theseparated conductors inthe horn region. These posts may be made ofdielectric material 9, as shown in Fig. 7a, or may be of metallicmaterial 8 as shown in Fig. 7, depending upon whether capacitiveimpedance or inductive impedance is desired to obtain the match betweenthe transmission system and free space. The position and thickness ofthese posts may be calculated to obtain the desired dielectriccharacteristic. While in this embodiment the dielectric 3 is shownterminated at the small end of the horn, it may be continued out to thelarge end of the horn.

Figs. 8, 9, and 10 show two line conductors 10 and 11 proximate a singleground conductor 12, separated by two layers of dielectric material 13and 14, whereby a double horn array is obtained. As is well-known in theart, an array of two or more electromagnetic horns will provide asharper directivity pattern than that of a single horn. The taper 1S, 16in thickness of dielectric is linear with distance, although the ilare17, 1S in width of the line conductors 1t) and 1l and the Hare 19 in theground conductor i2 are shown to be exponential. The exponentialvariation in width of the conductors is for the purpose of providing asmooth match between the impedance of the transmission system and thatof free space. The energy source is shown to energize both the lineconductors in phase with respect to ground.

in Pig. l1 a horn array is shown comprising effectively four horns 2l,22, 23, and 24 in a. single array, each provided with an exponentialvariation in thickness of the dielectric 32 between the line conductorand the ground conductors. Horn 2i comprises line conductor 26 andground conductor 27, horn 22 comprises line conductor 28 and groundconductor 27, horn Z3 comprises line conductor 225 and ground conductor29, and horn 24 comprises line conductor Sti and ground conductor 29. Asource oi energy 3l is connected across the line and ground conductorsin parallel. In such an array it is clear that there are a number N ofline conductors, a number N-l of ground conductors and a number of N-l-lof dielectric layers 32. The exponential variation 2S in thickness ofthe dielectrics is shown to be asymmetrical between a given pair of lineand ground conductors rather than symmetrical as shown in Fig. 4, butdue to the face that an even number of horns is used, the net effect isto obtain a symmetrical pattern in space due to the back-to-backarrangements of the variations in thickness. The directivity pattern ofsuch an array will be sharper than that of the array shown in Figs. 8,9, and l0 and still sharper than that of the single horns shown in Figs.l through 7. Tt will be clear that arrays similar to that of Fig. ll maybe constructed by utilizing a greater number of horns and that moredirective eld patterns may be so obtained. It will also be clear thatthe variation in width of the line and ground conductors may beexponential as shown in Fig. 8 or linear as shown in Figs. 2 and 6. itwill also be clear that matching posts similar to those shown in Figs.6, 7, and 7a may be employed in the region of variation in thickness ofdielectric.

While I have described above principles of the invention in connectionwith specific apparatus, it is to be clearly understood that thisdescription is made only by way of example and not as a limitation tothe scope of the invention, as set forth in the objects thereof and inthe accompanying claims` I claim:

l. An electromagnetic horn comprising rst and second elongatedstrip-like conductors, dielectric means including solid dielectricmaterial separating said conductors in closely spaced substantiallyparallel relation, said second conductor being wider than said rstconductor to present thereto a planar surface whereby the electric fieldof radio frequency energy propagated along said conductors isconcentrated therebetween similarly to the iield distribution of the TEMmode, said conductors being terminated for end-tire radiation, said rstconductor having a first part of uniform width and having a second partadjacent the terminated end thereof iiared outwardly in a plane parallelto said planar surface to provide in conjunction therewith an open.sided horn, and a characteristic of said dielectric means being variedfrom a point in saidv horn toward the large end thereof` to provide animpedance transition between said conductors and free space.

2. An electromagnetic horn according to claim l, wherein the dielectricmaterial is in the form oi' a layer and the variation in the dielectriccharacteristic is a variation in the thickness of said layer.

3. An electromagnetic hornA according to. claimA 2, wherein saidvariation` of thickness is exponential.

4. An electromagnetic horn according to claim 2, wherein said variationof thickness is a linear variation.

5. An electromagnetic horn according to claim 2, wherein the variationin thickness of the layer of dielectric is symmetrical with respect tothe mid-plane between said conductors.

6. An electromagnetic horn according to claim 3, wherein the variationin thickness of the layer of dielectric comprises a tapering of thedielectric from a maximum thickness from a given point in said horn to aminimum thickness adjacent the large cnd of said horn.

7. An electromagnetic horn according to claim l, wherein the variationin the dielectric characteristic includes the provision of posts ofmetallic material disposed between said conductors.

8. An electromagnetic horn according to claim l, wherein the variationin the dielectric characteristic includes the provision of posts ofdielectric material disposed between said conductors in the area of theared part of said rst conductor.

An electromagnetic horn according to claim l, wherein both said firstand second conductors are llared to provide said horn.

lt). An electromagnetic horn array comprising a pair of line conductorsof elongated form spaced apart in substantially parallel relation, anelongated ground conductor disposed mid-way between said lineconductors, said ground conductor being wider than either of said lineconductors to present to each of said line conductors a planarconducting surface whereby the electric field of radio frequency energypropagated along said conductors is concentrated between each lineconductor and the adjacent planar surface of said ground conductorsimilarly to the iield distribution of the TEM mode, and each of saidline conductors having a part adjacent the end thereof Hated outwardiyin a plane parallel to said ground conductor to provide therewith twoadjacent open sided horns.

ll. An electromagnetic horn array according to claim l0, wherein thespacing between the conductors includes dielectric material and whereina characteristic of said dielectric material is varied from a pointwithin each horn toward the large end of cach horn to provide impedancetransition between the conductors and free space.

l2. An electromagnetic horn array according to claim ll, wherein thedielectric material is in the form of layers, and the variation in thedielectric characteristic thereof is a variation in the thickness ofsuch layers.

13. An electromagnetic horn array according to claim l2, wherein thevariation in thickness of the layer of dielectric material issymmetrical with respect to the ground conductor.

14. An electromagnetic horn array comprising a number N of lineconductors, a number N-l of ground conductors, a number N+1 ofdielectric means separating said line and said ground conductors, saidground conductors being wider than said line conductors each of saidline conductors having a part adjacent the end thereciC ilared outwardlyin a plane parallel to said ground condoctor to provide therewith anopen sided horn, and a characteristic of said dielectric means beingvaried toward the large end of said arcd line conductors to providesubstantially smooth impedance transition between said conductors andfree space.

l5.` An electromagnetic horn array according to claim 14, wherein saiddielectric means comprises layers of solid dielectric, and the variationin the dielectric chat'- acteristic includes a variation of thedielectric layers with the variation being substantially symmetricalwith respect to the ground conductors.

l6. An electromagnetic horn array according to claim 14, wherein all theline and ground conductors are flared to provide the horn effects.

l7. In an electromagnetic radiation system, a transmission linecomprising rst and' second elongated conductors and a layer ofdielectric material disposing said conductors in substantially parallelspaced relation, said second conductor being wider than said rstconductor to present to said rst conductor a planar conducting surfacewhereby the electric field of radio frequency energy propagated alongsaid conductors is concentrated therebetween similarly to the fielddistribution of the TEM mode and said first conductor having a firstportion along its length of uniform width and a second portion flaredoutwardly in a plane parallel to said second conductor toward the outputend of said conductors to provide in conjunction with said secondconductor an impedance transition between the transmission path providedby said conductors and free space.

18. In an electromagnetic radiation system according to claim 17,wherein the characteristics of said layer of dielectric material arevaried from a point between said conductors toward the output end ofsaid conductors.

19. In an electromagnetic radiation system according to claim 18,wherein said characteristic variation comprises a variation in thethickness of said layer of dielectric material.

20. In an electromagnetic radiation system according to claim 18,wherein said characteristic variation comprises a tapering of said layerof dielectric material toward the output end of said conductors.

References Cited in the file of this patent UNITED STATES PATENTS HolmanMay 28, King May 26, Dallenbach et al. Sept. 29, Katzin Apr. 9, JohnsonDec. 30, Jaynes May 18, Iams June 8, Brillouin Nov. 30, Wheeler May 23,Barrow Feb. 27, Lindenblad June 5, Rosencrans Dec. 4, Kock Dec. 4, WileyMay 13, Kock June 10, Jaffe July 29, Bliss Sept. 23,

FOREIGN PATENTS Great Britain Nov. 23, France Feb. 4, Norway July 23,

